Behind the scenes

Although this spell and Wingardium Leviosa are seemingly the same spell, they are not. The Hover Charm makes the target hover, statically, whereas Wingardium Leviosa makes objects fly, the caster having some degree of control of where they fly to.

On Pottermore, the cake only hovers for fourteen seconds before smashing; such may indicate that the spell has a time limit. However, it is more likely that Dobby only waited fourteen seconds before dropping the cake.

This spell and Levioso have curiously similar effects; it may be that the two are the same, or potential variants.